We assessed the efficacy of prolonged interferon-alpha (IFN) therapy in children with chronic hepatitis caused by hepatitis delta virus (HDV) by treating 26 paediatric cases with IFN-alpha 2b (5 MU m-2, then 3 MU m-2 three times weekly for 12 (medium-term group MTG) or 24 months (long-term group, LTG).